Ball roller bearings are rolling bearings with special rolling elements which are designed as ball rollers and which, starting from a basic spherical shape, have in each case two side faces which are flattened from this basic spherical shape and are arranged parallel to one another and between which the running surfaces of the ball rollers are in each case arranged. Ball roller bearings of this type have long been known in various embodiments, for example, from DE 311 317 A or DE 42 34 195 A1 and are distinguished, above all, in that, by virtue of the special design of their rolling elements, as compared with ball bearings of identical type, either they can be filled with a larger number of rolling elements and thereby have a higher load-bearing capacity (upgrading) or can he designed with the same load-bearing capacity and at the same time require a substantially smaller radial construction space (downsizing). Another advantage of such ball roller bearings is that, by virtue of their rolling element shape, either they can be designed to be substantially narrower axially than comparable ball bearings and thereby contribute to a saving of axial installation space or they can be designed axially with the same width as comparable ball bearings and consequently have a substantially larger lubricant reservoir and a longer service life.
Furthermore, it is known from DE 10 2005 014 556 A1, in such ball roller hearings, to design the width of the ball rollers between their side faces with about 70% of the diameter of their basic spherical shape, since the ball rollers thereby have a contact face with their raceways in the bearing rings, such as the balls of conventional grooved ball bearings also have with their raceways. Moreover, in practice, such a width has proved to be an optimum in terms of the radial and axial load-bearing capacity of the ball roller bearing and makes it possible that a large number of ball rollers can be introduced into the ball roller bearing by the eccentric or axial mounting method.
Furthermore, DE 102 10 670 B4 has disclosed a method for producing the rolling elements of a ball roller bearing, the rolling elements of which are designed as ball rollers which additionally have on their side faces in each case a circular end trough as a lubricant reservoir. According to this method, the ball rollers are produced in that, first, a multiplicity of blank segments are cut off in a defined length from a round wire of defined diameter and are then converted by compression molding in the form of a closed die into ball roller blanks having end troughs. Since, during this compression molding, because of an excess of volume of the blank segments in relation to the shape of the die, a saturn ring, as it is known, occurs at the raceway transition from one ball roller half to the other ball roller half, this saturn ring is removed in a fourth method step with the aid of a separate tool after the ball rollers have been ejected from the closed die. Finally, the grinding of the ball roller blanks to the desired final dimensions is carried out in a vertical ball grinding machine which is designed with a vertically arranged fixed grinding wheel and with a rotating grinding wheel arranged parallel to the latter and in both grinding wheels has, in each case opposite one another, an identical number of grinding grooves arranged coaxially to one another. In a continuous rotary process, the running surfaces of the ball rollers are ground circularly between these grinding wheels, while, in order to increase accuracy, grinding is carried out together with conventional bearing balls of identical size which have previously been intermixed in a preferred ratio of size and which have previously been intermixed in a preferred ratio of 25% ball rollers to 75% bearing balls.
In such a production method, however, it has proved to be a disadvantage that, during the compression molding of the ball roller blanks, said saturn ring occurs at the raceway transition from one ball roller half to the other ball roller half and first has to be removed again in a complicated way with the aid of a separate tool and therefore needlessly increases the production costs for the ball rollers on account of further necessary manufacturing steps and additional tool costs. Furthermore, the occurrence of such a saturn ring also has the disadvantage that all the material fibers underneath its surface are also aligned with its course, and therefore, after the removal of the saturn ring, a material fiber course occurs which is directed perpendicularly to the running surface of the ball rollers and has an adverse effect on the component strength and loadability of the ball rollers.
Another disadvantage is that the grinding of the ball rollers to their final dimensions is carried out in a vertical ball grinding machine, with bearing balls of identical size being intermixed, since this may cause the ball rollers and bearing balls to fall one on the other within the grinding grooves in the grinding wheels as a result of gravity, this leading to impact damage to the ball rollers or their running surfaces which can no longer be rectified during grinding because intended final dimensions are to be maintained. At the same time, by the ball rollers being intermixed with bearing balls in a ratio of 25:75 per grinding process, only very small batch sizes can be produced which, in conjunction with process times of up to 150 hours per grinding operation, contribute to a further adverse rise in the production costs for the ball rollers.